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- What are the hardware and software requirements for running the model?
- You must have access to the Internet and a web browser that supports JavaScript, such as
Netscape Navigator 2.01 or Internet Explorer 3, or later versions. Your
hardware and software requirements will be determined by your Internet access and browser
software.
- Why can't I get the model to work?
- The most common problem is that your browser does not support JavaScript. You must
use Netscape Navigator version 2.01 or Internet Explorer 3, or later versions to run this
model. Due to the practice of releasing alpha and beta versions of their software, there
are many different versions of Netscape Navigator version 2 around. Early alpha or beta
test versions may not work with JavaScript. I would suggest that you check your exact
version number. This can be done by looking at About Netscape... under the Help menu. If
you have an alpha or beta release, you will need to get a newer version.
- Can I use commas in the input fields?
- No. In many countries, it is common practice to use a decimal comma instead of a decimal
point. Unfortunately, in JavaScript you have to use the decimal point, regardless of which
country setting you have in your operating system. In JavaScript, only digits after a
decimal comma will be used for calculations, which will produce incorrect results.
- When I print the model, why do I get blanks in the input/output fields?
- This is a known bug in Netscape Navigator versions 2 through 2.02 for Windows. When
printing forms, only the form labels appear, not the user-input text or the radio buttons.
There are two solutions to this problem. 1) Upgrade to version 3 or later of Netscape
Navigator. 2) Use the Alt-Print Screen keys to copy the window, then paste it into another
application such as Paintbrush and print from there.
- I can view the model and enter data in the form but when I hit the recalc
button, nothing happens.
- It is possible that your browser does not support JavaScript. You must use
Netscape Navigator version 2.01 or Internet Explorer 3. Older versions of Netscape and
other browsers will allow you to view the forms but will not execute the JavaScript code
necessary to calculate the model. It is also possible that JavaScript has been disabled.
Check your browser settings to be sure that JavaScript or JScript is enabled.
- Why can I edit the data in the output areas and what effect will this have on my
results?
- The models use the HTML forms interface for both input and output. With the current
version of JavaScript, there is no way to distinguish between input fields and output
fields and prevent users from entering or changing data in the output. If you type data in
the output fields, it will not effect any other fields. Also, when you hit the recalc
button, any data you have entered in the output fields will be replaced with calculated
data.
- How does the model get recalculated?
- There are several ways to recalculate the model. The easiest way is to simply change the
data in one of the input fields. In order to effect a change in a text field, you must hit
the tab key or select another field with the mouse after you have typed in new data. Note
that hitting the return key will not cause a recalc. You can also recalc by clicking on a
radio button or check box, or by changing the selected item in a drop-down list. Finally,
you can recalc at any time by clicking on the recalc button.
- How can I save my work?
- The best way to save your work is to print it out. For security reasons, JavaScript does
not permit data to be saved or retrieved from the client computer. Using the File Save
as... function in Netscape will save a copy of the HTML document to your disk, but the
data you have entered will be lost. Netscape does save the data you have entered in a
cache, so you will probably not lose your data if you go to a different URL and then
return to the model, as long as you do not quit Netscape.
- Why do some of my results have a lot of trailing zeros or nines to the right of
the decimal place?
- There appears to be a bug in the JavaScript rounding function that sometimes causes
extremely small errors to show up in rounded numbers. These errors appear at about 15
places to the right of the decimal, so they should not materially effect any calculations
in the model unless you are working with extremely small numbers.
- What should I do if I get a JavaScript error message?
- Congratulations! You've probably found a bug in the model that I was not aware of. Send
me an email message at kelley.j.cyr1@jsc.nasa.gov.
Your message should include: the name of the model you were using, the exact wording of
the error message, a description of what you were doing at the time the error occurred,
any data that you had entered in the model, the name and version number of your browser,
and a brief description of the computer system you are using.
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